Offit is the chief of the infectious diseases unit at Children’s Hospital of Philadelphia, and has written extensively about the perils of taking the massive doses of vitamins that are routinely sold in health food stores. Part of the problem, he thinks, is that since the vitamin industry is not regulated people remain unaware of the dangers. Offit recently told the Guardian [2]: “Were the FDA to actually regulate this industry, I think megavitamins would have a black box warning on them. But they don’t — the consumer doesn’t know about many of the risks.”

Offit traces the vitamin craze to one of last centuries’ greatest scientists and humanitarian figures: Linus Pauling. Pauling won the Nobel Prize at the age of thirty for redefining the nature of chemical bonds, and followed that up by founding the field of molecular biology and making seminal discoveries in paleontology and evolutionary biology. He went on to win another Nobel, this time the Peace Prize for promoting the Nuclear Test Ban Treaty. But then he started promoting excessive amounts of vitamin C as a panacea that could cure everything from the common cold to cancer. He wasn’t a shyster or anything — he himself took 18,000 milligrams of vitamin C daily, three hundred times the recommended daily allowance.

Pauling and his followers through the decades attributed vitamins’ miraculous properties to their antioxidant qualities. The process of making energy from food that occurs in the mitochondria within our cells is called oxidation, because oxygen is required in the chemical reaction. Oxidation generates free radicals, molecules that are desperate to react with almost any other molecules they can find. These free radicals, formed as a normal byproduct of normal cellular metabolism, are so highly reactive that they can damage DNA, cell membranes, and the linings of arteries. They have thus been implicated in aging, cancer, and heart disease.

Vitamins — especially vitamin A, vitamin C, and vitamin E, as well as selenium and beta-carotene — are high in antioxidants, which, as their name suggests, neutralize free radicals. The logic thus goes like this: free radicals damage DNA, so they’re bad. Antioxidants fight free radicals, so they’re good. Vitamins have antioxidants, so therefore we should take outrageous amounts of vitamins. This line of reasoning successfully sells not just pills, but foods and face creams as well. You can’t have too much of a good thing, right? And vitamins are “all natural,” so taking more of them can’t hurt, right?

Unfortunately, wrong and wrong. Study after study has shown that ingesting megadoses of vitamins has at least one pretty serious side effect: death. In 1996, one study had to be ended abruptly because subjects who were given vitamin A or beta-carotene were dying of cancer and heart disease at rates 28 and 17 percent higher, respectively, than those who received neither — so it was not ethical to continue giving the vitamins and supplements. Just last year, a Cochrane review concluded that “beta carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A” [3]. Cochrane reviews examine all of the existing primary research on a topic (that meets certain criteria, like being a fair trial) to establish whether or not there is conclusive evidence about a specific treatment. They are internationally recognized as the highest standard in evidence-based health care.

It’s unclear why the logic doesn’t hold up. Perhaps free radicals aren’t as bad as they sound. Perhaps the antioxidants we make are sufficient to counteract the free radicals, and we are ingesting much too much of a good thing. In this case, it is the vast imbalance between the antioxidants and free radicals in our bodies that explains why taking your vitamins can in fact hurt.

We certainly need vitamins; without enough, we end up with nasty diseases like scurvy and rickets. But humans are omnivores, and the vitamins we get from eating a balanced diet with lots of fruits and vegetables — the foods richest in antioxidant vitamins — are probably sufficient. Even popping a daily multivitamin that provides the recommended daily allowance just in case we’re not eating as well as we should is ok, Offit allows. But a typical vitamin E preparation from GNC has 33 times the recommended daily allowance — each pill thus contains the amount of vitamin E in 1,700 almonds, and almonds are a good dietary source of vitamin E! Each 1,000 mg tablet of vitamin C that people take when they have a cold contains the same amount found in eight whole cantaloupes. It is easy to mindlessly pop one of those pills daily, but thinking of them as 1,700 almonds or eight cantaloupes highlights how unnaturally excessive, and unhealthy, these doses are. With vitamins, as with so many other things in life, more is definitely not always better.